# Thread: Solving inequalities involving ln

1. ## Solving inequalities involving ln

, x (is a member of) [0,10]
I started off by doing this
2x+1>e^(3cos(x))
dont know how to proceed.

2. ## Re: Solving inequalities involving ln

Originally Posted by kandyfloss
, x (is a member of) [0,10]
I started off by doing this
2x+1>e^(3cos(x))
dont know how to proceed.
What exactly is the question? Solving the given inequality? What were the instructions? It cannot be solved by hand. You are obviously expected to use technology such as a graphics calculator to draw the graphs of y = ln(2x + 1) and y = 3cos(x) and then get an approximate solution.

3. ## Re: Solving inequalities involving ln

Yes, sorry i forgot to mention that. it asks you to solve the inequality.
Here's my graph. I see ln(2x+1) > cos(x) when x>1 , right?

4. ## Re: Solving inequalities involving ln

Yes, but you should graph 3cos(x).

5. ## Re: Solving inequalities involving ln

Originally Posted by kandyfloss
Yes, sorry i forgot to mention that. it asks you to solve the inequality.
Here's my graph. I see ln(2x+1) > cos(x) when x>1 , right?
You need to zoom in a lot better than that since it's close to 1.5 where they cross. Note also what happens around $x = 2\pi$

6. ## Re: Solving inequalities involving ln

Originally Posted by kandyfloss
, x (is a member of) [0,10]
I started off by doing this
2x+1>e^(3cos(x))
dont know how to proceed.
look at the graph of $y = \ln(2x+1) - 3\cos{x}$ over the given interval and note where $y > 0$